Congestive heart failure occurs as a result of impaired pumping capability of the heart and is associated with abnormal retention of water and sodium. It results in an inadequate supply of blood and oxygen to the body's cells. The decreased cardiac output causes an increase in the blood volume within the vascular system. Congestion within the blood vessels interferes with the movement of body fluids in and out of various fluid compartments, and they accumulate in the tissue spaces, causing edema.
The angiotensin converting enzyme inhibitor captopril has been approved by the United States Food and Drug Administration for the treatment of congestive heart failure. In many cases it is utilized in patients receiving digitalis, as well as diuretic treatment. The angiotensin converting enzyme inhibitor enalapril maleate has been approved by the United States Food and Drug Administration as adjunctive therapy in the management of heart failure for use along with diuretics and digitalis.
Delaney et al. in U.S. Pat. No. 4,722,810 disclose enkephalinase inhibiting compounds of the formula ##STR2## wherein R.sub.1 is hydrogen or acyl; R.sub.2 is lower alkyl, aryl, aralkyl, heterocycloalkyl, or cycloalkylalkyl; R.sub.3 is hydrogen, lower alkyl, aryl, aralkyl, heterocycloalkyl, or cycloalkylalkyl; n is an integer from 1 to 15, and R.sub.4 is hydroxy, lower alkoxy, aralkoxy, etc. Delaney et al. in U.K. Patent Application 2,207,351A disclose that such compounds possess neutral endopeptidase inhibitor activity and produce diuresis, natriuresis, and lower blood pressure. Delaney et al. in U.K. 2,207,351A also disclose that the neutral endopeptidase inhibitors can be administered in combination with other blood pressure lowering agents, for example, an angiotensin converting enzyme inhibitor such as captopril, zofenopril, fosinopril, enalopril, lisinopril, etc.
Cavero et al., "Cardiorenal Actions of Neutral Endopeptidase Inhibition in Experimental Congestive Heart Failure", Circulation, Vol. 82, p. 196-201 (1990) reported that the administration of the neutral endopeptidase inhibitor SQ28,603, i.e. (N-[2-(mercaptomethyl)-1-oxo-3-phenylpropyl-.beta.-alanine), in anesthetized dogs with congestive heart failure induced by rapid right ventricular pacing resulted in diuresis and natriuresis. The authors conclude that these studies support an important therapeutic role for neutral endopeptidase inhibitors in congestive heart failure.
Haslanger et al. in U.S. Pat. No. 4,749,688 disclose the method of treating hypertention with neutral metalloendopeptidase inhibitors alone or in combination with atrial peptides or angiotensin converting enzyme inhibitors. Haslanger et al. in U.S. Pat. No. 4,801,609 disclose mercaptoacylamino acids useful in the treatment of hypertension and congestive heart failure.
Delaney et al. in European Patent Application 361,365 Al disclose that neutral endopeptidase inhibiting aminobenzoic acid compounds produce diuresis, natriuresis, and lower blood pressure and are additionally useful in the treatment of congestive heart failure. Delaney et al. further disclose that these neutral endopeptidase inhibitors can be administered in combination with other blood pressure lowering agents such as angiotensin converting enzyme inhibitors, i.e., captopril, zofenopril, fosinopril, enalapril, lisinopril, etc.